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 A057838 Numbers n such that A055079(n) = 2^n. 3
 2, 3, 11, 35, 71, 191, 419, 659, 1091, 1199, 1379, 1655, 2015, 2135, 2339, 2591, 3059, 4439, 6119, 6215, 6335, 7055, 8099, 8351, 8519, 9815, 11159, 12419, 12431, 12599, 12719, 12851, 13679, 15119, 15239, 16415, 16919, 17255, 17879, 18215, 18479 (list; graph; refs; listen; history; text; internal format)
 OFFSET 1,1 LINKS Ray Chandler, Table of n, a(n) for n = 1..13925 FORMULA 2^a(n) = A057841(n) = A055079(a(n)). A001221(A055079(a(n))) = 1. EXAMPLE 11 is here: 2^11 has 11 nonprime divisors; c(11)=A055079(11) could not have r=2, 3, 4 or more distinct prime divisors because 11 + {2, 3, 4, 5, 6, 7, 8, 9, ...} values of corresponding d(c(11)) = {13, 14, 15, ...} had 1, 2, 2, 4, 1, 3, 1, 3, 2, 2, 1, 4, 2, 2 non-distinct prime divisors which provides upper bound for r ... in contradiction with demanded values: 2, 3, 4, 5, 6, 7, ... This is why A055079(11)=2048. Larger cases are handled in a similar way. a(35) = 15239 since A055079(15239) = 2^15239 which has 4588 decimal digits. A protocol for 15239 is as follows: u=15239; t0=Table[s, {s, 0, 17}]; t1=Table[mr[w], {w, u, u+17}]; t2=t1-t0; g=Table[{w, mr[w]}, {w, u, u+17}]; i1=TimeUsed[]; Write["a(bad)tx1", u, t1, t2, g]; 15239. Supposed number of A001221(x) which should be larger or equal than A001222(d(x)): {0, 1, 2, 3, 4, 5, 6, 7, 8, 9, 10, 11, 12, 13, 14, 15, 16, 17}. A001222(d(x)) {3, 6, 1, 2, 2, 4, 2, 6, 2, 5, 4, 5, 2, 5, 2, 3, 5, 4}. A001222(d(x)) - A001221(x) (negative value means "nasty case") {3, 5, -1, -1, -2, -1, -4, -1, -6, -4, -6, -6, -10, -8, -12, -12, -11, -13} numbers (corresponding d(x) values for some x) together with A001222[d(x)] {{15239, 3}, {15240, 6}, {15241, 1}, {15242, 2}, {15243, 2}, {15244, 4}, {15245, 2}, {15246, 6}, {15247, 2}, {15248, 5}, {15249, 4}, {15250, 5}, {15251, 2}, {15252, 5}, {15253, 2}, {15254, 3}, {15255, 5}, {15256, 4}}. CROSSREFS Cf. A055079, A001221, A001222, A000005, A058060, A058061, A057841. Sequence in context: A296005 A159458 A305846 * A219497 A006497 A038912 Adjacent sequences:  A057835 A057836 A057837 * A057839 A057840 A057841 KEYWORD nonn AUTHOR Labos Elemer, Nov 24 2000 EXTENSIONS Edited, corrected and extended by Ray Chandler, Aug 14 2010 STATUS approved

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Last modified April 19 08:26 EDT 2021. Contains 343110 sequences. (Running on oeis4.)